Three-Dimensional Simulation of Bulge Formation 1n Contact Hole Metalization

During sputter deposition of metal layers bulges at sharp convex corners can arise and are observed after metalization of contact holes for semiconductor circuits. We present an explanation of this phenomenon by assuming that in process steps prior to the deposition a ledge is formed . This assumption together with the choice of an appropriate model for the distribution of the incident particles explains the evolution of the resulting film profile including the bulge at the topmost convex corner of the structure. The profile is simulated for several positions on the wafer. The variation of bulge shape and film thickness depending on the orientation of the sidewalls for the peripheral positions is reproduced. We investigate the geometry and particle flux conditions and show simulation results for different geometries contact hole diameters, aspect ratios and an' . gles of incidence. Simulation results are compared with SEM pictures obtained from experiments.